Story County, Iowa: drinking water report. Story County in central Iowa has about 98,000 residents, including Ames and Iowa State University.
Story County in central Iowa has about 98,000 residents, including Ames and Iowa State University. The City of Ames draws from the Skunk River and a series of alluvial wells, while surrounding communities rely on groundwater from the glacial drift aquifer. Iowa's intensive row crop agriculture – corn and soybeans cover the vast majority of the county – defines the water quality challenges.
Nitrate is the primary concern. Ames Water Treatment Plant regularly processes raw water with nitrate concentrations above the MCL of 10 mg/L during spring, requiring blending with lower-nitrate sources or ion exchange treatment. According to the Iowa DNR's 2024 drinking water compliance data, the Ames system's raw water nitrate peaked at 14.2 mg/L in May 2024 following heavy spring rains that flushed fertilizer from surrounding fields.
Atrazine follows a similar seasonal pattern, with spring flush concentrations occasionally approaching the MCL of 3 ppb. A 2024 Iowa Geological Survey study found that 30% of private wells in Story County's glacial drift showed nitrate above 5 mg/L, indicating widespread agricultural contamination of the shallow aquifer.
Iowa's agricultural intensity means nitrate is not a hypothetical concern – it is a seasonal operational challenge that Ames Water actively manages. The treatment plant handles it, but private well owners outside the municipal system do not have that protection.
Check your water for current data. For nitrate, reverse osmosis is the most reliable household solution. Our water filter guide ranks systems by certified nitrate removal. Pull your detailed report for seasonal patterns, and visit our Iowa page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Story County, IA.
The EPA places Story County, IA in Zone 1 - the EPA's highest-risk category, where the predicted average indoor radon level is above 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
47% of homes in Story County, IA were built before 1980, and 17% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Story County, IA averages 6.8 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide